The Single Most Common Carburetor Problem (Clogged Pilot Jets) and How To Fix It | MC GARAGE

There are a LOT of things that can go wrong with carburetors, but more often than not running issues (like hard starting, bogging off idle, or a hanging idle) are caused by the same issue: the pilot jet. This video isn’t a comprehensive troubleshooting guide (that would be an hour-long episode), but it does address the single most common carb issue. Hopefully it helps you.

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A motorcycle carburetor is just a mechanical mixing device. It mixes gas from the float bowl with air passing through the throat in a precise ratio, and if that fuel/air ratio is off, you're going to have problems.

Far and away the most common problem carb problem is clogged pilot jets. The pilot jet, along with the mixture screw, are what make your bike run at idle on up until about quarter throttle, so that’s where you should look if your bike is hard to start or only runs with the choke on, bogs or stalls as you crack the throttle open, or has an idle that revs up on its own or “hangs” at a high idle before settling down.

All of these issues are indicative of a lean running condition, meaning that fuel/air ratio has too much air and not enough fuel.

More likely than not your pilot jets are jammed up with debris or gummy gas, and cleaning it means pulling the carb or carbs off your bike. Then you’re going to need to pop off the float bowl and clean the pilot jet, which is typically the smaller of the two brass jets visible on the bottom of the carb. Often it’s removable, so you unscrew it and blast it out with solvent and compressed air.

While you have the carb off your might as well give the thing a thorough cleaning, so click here to see our MC Garage video with step-by-step instructions for a complete carb cleaning.

So why is the pilot circuit such a common problem? Because it’s got the smallest passageways in the carburetor, so they’re the first to clog. Pump gas now has a bunch of ethanol in it and it starts to go bad and gum up in just a matter of weeks, so if you’re not riding your bike regularly you can save yourself a lot of trouble by adding a fuel stabilizer to keep the gas from degrading.

There is one other thing that can cause a lean condition at idle, and that’s an air leak. If your bike has rubber intake boots or relies on an o-ring or gasket to seal the carb to the flange or the flange to the cylinder head, that’s also something to check. But the majority of the time, it’s just an issue with the pilot circuit.

[flyingmerkel]

When blasting out your pilot jet, hold on real tight so it doesn't go shooting across the garage and land behind the impossible to move workbench.

[RandomGuyDan]

Good video Ari, but I do have 3 comments:

(1) When spraying carb cleaner through the pilot jet make sure that you do a couple of sprays with your finger over the bottom exit hole so that you can make sure the side holes are also clear. You want to see a nice strong mist of solvent coming through.

(2) If the jet is completely clogged often no amount of solvent will clean it. Before I pull a carb for cleaning I hit my local guitar store for a piece of steel E string . They will usually have some left over from stringing jobs and will typically give it to you for free. This is very fine but very stiff wire and you can gently work it through the jet without damaging it. Once there is a passage through the jet, the high pressure cleaner will then remove the rest as it passes through.

(3) I HIGHLY recommend holding the jet in a towel before you blow compressed air through it. Often your fingers alone won't hold it strongly enough and you can blow it across your garage never to be seen again (ask me how I know, LOL).

[hommebizzare]

This video series is great. In fact, the worst thing about it is the time between episodes

[m_s]

I just found this channel yesterday, watched about 6 hours worth of content so far. Your videos are insanely well done guys.

[xfire]

Never really a problem until Mr. Ethnol cam along .

[Josh-zylq]

This video was not “very brief” it was informative and not too long. Usually these videos are unorganized. This was not too long. Keep it up ! 👍

[rubenotero]

I've been intimidated by how complex carbs look for a long time, but this video was very informative and I definitely have everything I need to clear out my pilot jets

[PeterisKelle]

Thank you so much for this video! You saved me more hours of figuring out what was happening with my Honda Dominator, that it just didn't start (only by using starting fluid). Checked almost everything (fuel, spark, battery, measured stator, pulse generator, coil, electricity contacts, CDI box contacts, vacuum leaks around carb and air box, etc.), especially after disassembling and cleaning carb. In the end your video made me think that it still might be a carb related issue, because I started to remember that the problem started when I switched the fuel tank petcock to RESERVE. Removed the petcock and yeap - there were some debris on the bottom of the tank, without original fuel filter, which clogged the pilot jet. After blasting out the pilot jet with an air gun and assembling everything back together, Dommie now runs just great! Thanks!

[chidori]

"...or the bottom."

Smooth.

[redryder]

thank you for this fan-freaking-tastic video series because of this video series you have given me the confidence to perform maintenance on my motorcycle that I would normally have to pay a shop hundreds of dollars to do last March I put tires on my motorcycle front and rear 2000 CBR 600 F4 have a motion Pro balancing stand everything went off without a hitch this spring I am going to change the clutch thanks Ari

[wesjewell]

Thank you so much! This clears everything wrong with my bike and it worked flawlessly. I’ve never seen a “perfect” tutorial but this covered absolutely everything needed!

[johnbaxter]

Thank you, gave me the confidence to give it a try on my 4 inline carb, removed it all and followed it to clean the pilot. Bike started and held idle fine, so happy!!!

[seansoles]

Great little walk through on this most common issue. Appreciate you man!

[Scoottoots]

Ari, thanks. I really get benefit from your clear explanations. I have a 1984 Suzuki GR650 Tempter. A bit of an oddity, but then so am I at 66 years old doing my first more in-depth build.

I am doing some performance and styling mods on the Tempter. Carb, exhaust, and air box work, is key on the performance front. I definitely had some high hanging idle with no sign of air leaks at the engine-side boots. Most of the problems seemed related to the pilot system.

I've rejet'd the pilots by one size, raised the needles by one notch, and rejet'd the mains by three sizes, to work hopefully well with the new more open mufflers and opened out air box. Of course I cleaned the carb interiors while at it. Fingers crossed :-)

[xEMRDx]

Been watching these videos for years ever since my first motorcycle!

[NJOwens-ephf]

Great vid Mr Henning .. I just rebuilt my carbs this winter, with confidence inspired by your first carb video ..
Thanks Ari

[petar-boshnakov]

Damn Ari, you explain it so good that it almost feels easy to mess with it. Great videos.

[DaytonaRider]

My VFR400 was notoriously bad for this. Great video! People should really watch this and learn.

[behmer]

Thanks Ari! All your videos are great and really helpful

[goranahlvik]

Thanks, directly on how to fix the problem, no five minutes of talking :)